We plan to study the urinary and fecal elimination profiles of both oral and intravenous [14C-6] 5-FU and its metabolites in the presence of 776C85. Eight cancer patients will be randomly assigned to receive either an intravenous dose or an oral solution of 5-FU labeled with tracer amount of [14C-6] 5-FU given by an alternative route of administration in period two. In both periods, patients will receive oral 766C85. Urine, fecal and blood levels of 5-FU and its catabolites will be measured for 48 hours at regular intervals.